Dots on the road

I just know that it's going to be so obvious to everyone else, but I can't work it out......somebody put me out of my misery please........

On the Satnav map, there are small dots on the roads - not regularly spaced - sometimes distant, sometimes close together, sometimes in clumps.
I've tried and failed to match them to physical elements at that part of the road, and considered whether it reflects a measure of busyness, but I can't match it with anything.
any ideas ?

Dots on SAT NAV roads are normally 'Breadcrumbs', that is a trail left on your Sat Nav of your previous routes travelled.
I think they are there to help you find your way home.

https://en.wikipedia.org/wiki/Breadcrumb_(navigation)

they can be turned off, turn off tracking..

Thanks Ian4x4 - that makes sense now.